Potential recording marker



March 14, 1939. F. OFFNER POTENTIAL RECORDING MARKER 2 Sheets-Shet 1Filed Aug. 29, 1936 Jrzuen for ffrzer F. OFFNER POTENTIAL RECORDINGMARKER March 14, 1939.

Filed Aug. 29, 1936 2 Sheets-Sheet 2 in van 2'07" Frank 2171 OffrzSlim-FE or ies PYQTENTIAL RECQRDING MARKER Franhlin @finer @lncago,Application August 29, 3936:, Serial No. $8.5M

This invention is in that general class wherein electrically deformabledielectric materials are used for recording variations in electricpotential. In the past such uses included the deflection of light inoscillographs, and use in phonograph recorder. The present applicationof such a dielectric is intended mainly for work in medical research buthas numerous other applications in chemistry, physics, and engineering.in physiological work, for example, in recording the precise nature ofelectrical variations in heart action or muscle contractions, it hasbeen customary to make use of a beam of light deflected or produced inoscillographs and recorded on a moving photographic surface.

The present invention is the outcome of an attempt to avoid the delays,expense and inconvenience of photographic technique, and with that endin view it was found that a recording pen could be actuated directly bythe motion occurring in a dielectric upon a change of potential,provided the dielectric is of proper form and composition and isproperly mounted for the intended work and in mass and structure isbalanced with the electrical impedance arrangement of the circuit withinwhich it is placed. The mechanical and electrical characteristics of theassembly are such. as to minimize the efiect or the natural resonancesof the electro-mechanical circuit.

Previous attempts to make marked oscillo graph records directly onmoving paper, so far as knownhave made use or" electromagneticallyactuated pens which had numerous inherent deiects, particularly that ora rather low maximum. response frequency. "New, cy the use or anelectrically deformable dielectric, the maximum re sponse quency of thepen is increased to about three times t.- of the electromagnetic pensand renders the trument much more useiul for physiological studies. isalso highly eficient as only a minute driving power is required. Thehigh impedance of the dielectric driver allows it to he efiectivelycoupled to the output of most ordlnary vacuum tubes with good impedancematch.

- in magnetic driving systems the situation is entirely difierent asthere is difilculty in obtain ing sufficient current to actuate the penexcept by the use of more or less complicated circuits using a multitudeof large tubes to get suiiicient power. Also its low impedance makes themagnetic drive impractical to couple into the output of a vacuum tubethrough a condenser of any convenient size, for the purpose or" blockingout the direct current component oi the output.

The high impedance of the dielectric driver allows for coupling to theoutput of any vacuum tube supplying suificient voltage at the requiredpower (about one-half watt) through a Iil0de1'- ately sized condenser,and resistance; and no polarizing current or voltage is required inaddition to the impressed signal. The response amplitude is practicallyindependent of frequency up to about 200 cycles per second. Thus, with afrequency range greater than that or the string galvanometer asordinarily used it is possible to obtain satisfactory marked recordswithin the range required for biological work. This also renders theinstrument useful in many other sciences; for example, inrecordinginumber and amplitude of Geiger counter discharges.

The purpose or the invention may be accomplished by means of aconstruction and the circuit arrangement illustrated in the accompanyingdrawings in which:

Fig. l is a fragmentary plan view showing the crystal, its holder insection, and the pen and recording tape.

Fig, :2 is a side view of the construction shown in Fig. 1.

Fig. 3 is a plan view of the crystal indicating three corner insulatinglined supports for the crystal and one corner for transmitting motion tothe pen.

l is an enlarged sectional detail of the pen.

Fig. 5 is a diagram of an actuating circuit for the crystal in which isan impedance device and is the crystal and pen assemblies, as shown ies.1 and 2.

Fl e. ii, "1, and 8 are showing optional forms oi the impedance deviceas connected to the 'cen operating assembly. lg. is an enlarged detaildielectric unit.

carrying out the invention as before outlined,

toe hest dielectric substances now available for the purpose are of theRochelle salt type lami nated to provide plurality of crystal platescombined to term compact clock. larly suitable form is composed of fourplates each cut with parallel laces properly oriented with thecrystallographic axes of the crystals. electrodes which carry to thecrystal the electro-motive force needed to produce a mechanical motionfor operating the pen are applied in good electric contact to theopposite faces of the block. There are also thin metallic contactelements between the cpposediaces of the plates termini; bloat. .irccmanner the A particu- L 'on fixed insulating blocks 4.

,whichserves to conduct ink crystal block may be formed is thatdescribed in Patent No. 1,803,275.

In the drawings the crystal is shown as a rectangular block I composedof four plates 2. The crystal block is supported at the three corners itThe remaining corner 5 of the crystal carries a metal attachment 6 bywhich motion of this free end of the crystal is transmitted to arecording pen. The pen 7 is a fine capillary tube having a downwardlybent end 8 bearing on a strip of paper tape 9. The paper is fed, forexample, in a longitudinal direction as indicated by the arrow in Fig. 2by an electric motor drive equipped with a standard variable speed drivenot shown.

The pen element 1 is attached to a perpendicular, tubular pivot supportI l which passes through a fixed arm i2 forming bearings for the pen.The tubular element H is plugged at its lower end and at its upper endfits a flexible tube 53 from a supply not shown, to the pen. As appearsin Fig. 1,. the pen passes through a link I 4 by which the pen isconnected to a multiplying lever I5. The latter is fulcrumed at 16 tothe casing IT for the crystal block 2. The shorter arm in of lever I5 issecured to a flexible bar 19 connecting the lever with element 6. Thelink I is composed of a flexible portion 20 and more rigid reinforcementelements 2|.

This specific link provides the necessary freedom of motion without theuse of loose connections and yet is sufficiently rigid to transmitvibrations without loss.

The electrical connections for the irystal blocks are indicated at 23 inFig. 2. Fl'd l Fig. 9 it may be seen that the ii plates forming block Ihave aihxed electrodes M which may be tin foil and. these arealternately connected in parallel to the conductors 23.

The paper tape 5 is supported under I by a guide plate 25. The positionof the plate 25 with respect to the pen 1 is controllable by a screwadjustment 26 which controls the height of one end of the plate 25,while the other re mains fixed at pivot 21. The adjustability of thepaper tape 9 with respect to the pen '1 allows the pressure with whichthe pen. bears upon the tape to be readily controllable. This pressureis adjusted to give proper damping of the motion of the pen. Thismechanical damping of the pen in combination with electrical circuits ofFigs. 6, '7, or 8 is adjusted to give a response amplitude substantiallyindependent of frequency over as large a range as possible.

In Fig. 5 is shown a circuit by which the crys tal may be actuated by avacuum tube amplifier. The crystal and pen assembly is shownsymbolically at 28. 29 is a thermionic vacuum tube which may representthe last vacuum tube in a series of cascaded stages in an amplifier. Theinput circuit of the vacuum tube til is not shown nor is the circuit forheating the filament of said vacuum tube. 3i isthe plate supply hatteryfor 28, and 32, the plate resistor.

the pen A blocking condenser 33 is used to allow the output of 29 to beobtained without the direct potential from 3|. A high resistance 34 isshunt-- ed from the output of 33 to the filament ill, to by pass anysmall direct potential which might leak across 33. At 35 is shownsymbolically an impedance device interposed between the output terminals36 of the amplifier and the input terminals 23 of the crystal 1 of thecrystal and pen assembly 28. The purpose of the impedance deensures vice35 is, with the mechanical damping of the pen previously disclosed, toprovide as nearly as possible a uniform response amplitude independentof frequency.

At certain frequencies the electro-mechanical system composed of thecrystal and pen assemblies 28 will exhibit resonance. The instrumenthere disclosed will generally be used only up to frequencies slightlyhigher than the first resonant frequency. Because of the large effectiveinertia of the pen. and associated mechanical linkage system relative tothat of the crystal element, this resonant frequency will depend largelyupon the mass of the former and only slightly upon that of the latter.Then as this resonant frequency is approached, for a constant appliedpotential the response amplitude of the pen would normally beconsiderably greater than the response amplitude at lower frequencies.Similarly the electrical impedance presented at the input terminals 23will be disproportionately lower than at lower frequencies.

At Fig. 6 is shown a circuit which may be used for the impedance device35 and which takes advantage of this properly of the crystal. Here aresistor 22 is placed in series between the output terminals 36 of theamplifier and the input terminals 23 of the crystal. Now, as thefrequency applied to the input terminals of 35 approaches the resonantfrequency of the electromechanical system 23, then assuming that theapplied potential is constant, the current flowing between the inputterminals of 35 will increase and the potential drop in 36 will thusincrease, and thus decrease the potential applied to the terminals 23and consequently decreasing the amplitude of motion of the pen 1.

Thus, it may be seen that the interposition of the resistor between theoutput of the amplifier and the input of the crystal i will aid inproviding a more nearly uniform frequency response.

Instead of the simple resistance shown in Fig. 6 more complicatedcircuits can be used at 35 giving a still more nearly uniform frequencyrespouse. In 7 is shown a resistor 31, a parallel circuit composed of aninductance 38 and a resistor fill in series, both being shunted by acondenser til, all being connected in series as shown. The resistor 35?may simply be the inherent resistance of inductance 38. By properlyproportioning the components 3'1, 3B, 3.? and ll], the desired effect ofgiving more uniform frequency response may be obtained. In Fig. 8 isshown another circuit for accomplishing the same purpose. H is again. aresistor, 42 an inductor, is another resistor which again may be theinherent resistance of 42, and a condenser M. portion, or all, of theresistances 22, 3?, or 4] may be replaced by the plate resistanceinherent in the thermionic tube, such as 29, supplying the actuatingpotential.

While the impedance device 35 is shown in Fig. 5 as interposed between28 and a particular form. of vacuum tube amplifier, it is to beunderstood that these circuits may be used with anipllfiers of otherforms and with supplies other than vacuum. tube amplifiers.

"While as bcforementioned, the instrument has numerous uses inelectrical and physical fields. that as illustrated is especially usefulfor work such diagnosing the condition of the heart. For this work avacuum tube amplifier of which in Fig. 5 might represent the last tube,is used. The input terminals of this amplifier, which must have avoltage gain of approximately 1,000,000 times, will be placed at twoproper points of the subject's body. Then, as the subject's heart passesthrough one cycle of motion a potential will be developed across thesetwo points of the body. This potential will be amplified by the vacuumtube amplifier and finally applied to the input terminals 23 of thecrystal and pen assembly 28. The motion of the pen, 1 is recorded in inkupon the moving tape 9 giving a record on 9 as shown in Fig. 1 at 45. Bythe form of this record, which, as it will be seen, is imme diatelyobtained, the condition of the subject's heart may be diagnosed.Previously permanent records have been obtained by comparativelycomplicated and expensive apparati in which a permanent record isobtained on a moving photographic film which requires photographicprocessing before it is available" for use for diagnostic purposes. Theimproved method here disclosed provides a means for obtaininga permanentrecord immediately available by a more economical method.

I claim:

1. In a device for making a directly visible and readable marked recordof the wave form.

of a varying electric potential upon a movable record receiving surface,a movable record mark= ing member having a marking element adapted tomove freely laterally over said record receiving surface, actuatingmeans for said marking member comprising apiezo-electric crystal element deformable under the influence of an'applied electric field,mechanical connecting means betwcen'said crystal element and saidmarking member for moving the latter as a direct func= tion of themotion of the crystal element, said mechanical connecting. means withsaid mark-= ing member having large effective inertia relative to theeffective inertia of the crystal, an input circuit to the crystal forapplying an electric field of varying potentials and frequencies to saidcrystal, and a series resistance in said input circuit, said seriesresistance dissipating the most energy-at frequencies approaching thefirst electromechanical resonant frequency of the crystal systemcomprising the crystal element and associated marking member andmechanical connections, whereby to obtain substantially true readablereproductions of the wave form of potentials of any frequencies up toand slightly above the said first electromechanical resonant frequencyof the crystal system.

2. In a device for making a directly visible and intelligible markedrecord of the wave form of a varying electrical potential upon a movablerecord receiving surface, a movable record marking member having amarking element adapted to move freely over said record receivingsurface, actuating means for said marking member comprising apiezo-electric crystal element deformable under the influence of anapplied electric field, motion multiplying connecting means between saidcrystal element andsaid markin member for moving the marking member as adirect function of the motion of the crystal element, said markingmember and connecting meansproviding so great mass loading of theelectromechanical system that the first electromechanical resonantfrequency of said system is substantially independent of the mass of thecrystal element, circuit connections for applying an electric field ofvarying potentials and frequencies to said crystal element, means insaid circuit connections presenting a resistive source of potential tosaid crystal element said resistive means dissipating the most energy atfrequencies approximating the first electromechanical resonant frequencyof the system comprising the crystal element and associated markingmember and connecting means, whereby the record traced by said markingmember is a substantially true recording of the wave form of the saidvarying potential for all frequencies up to and slightly surpassing thefirst electromechanical resonant frequency of the systemcomprising thecrystal element and associated marking member and connecting means.

3. In a device for making a directly visible and legible marked recordof the wave form of a varying electric potential comprising a movablerecord marking element, actuating means for said marking elementcomprising a piezo-' electric crystal element deformable under theinfluence of an applied electric field, motion multiplying meansproviding a driving connection between said crystal element and saidmarking element, said motion multiplying means with said marking elementhaving large effective in ertia relative to the effective inertia of thecrystal

